Tetrazaindene compounds and photographic application



iemv.

No Drawing. Application October 3, 1957 Serial No. 687,864

11 Claims. (CLJ96-61) This invention relates to ,tetrazaindene compounds, methods for making them, and to photographic silver halide emulsions andphotographic treating baths contain.

ing them. h

Silver halide emulsions are frequently subject to image degradation during processing, that is, during development,

fixing, washing, toning, or other treatmentand during the moist heat to which they are subjected on drying, such-as when prints are subjected to ferrotyping or hot-type glazing. This degradation of the image frequently manifests itself as plumming or bronzing of the image.

It is also well known that photographic emulsions on storage tend to lose sensitivity and to become spontaneously developable without exposure to light. There is normally a detectable amount of the silver salt reduced during development in the areas where no exposure was given; this is commonly called fog, and sometimes called chemical fog where it is necessary to distinguish between it and the effects of accidental exposure to radiation; in this invention, I am not concerned with the latter.

Fog depends both on the emulsion and the conditions of development; for a given emulsion it increases with the United States Patent degree of development. With constant development conditions, it tends ton-increase with-time, temperature and relative humidity of storageconditions;itiscommon practice to make accelerated tests of the stability of photographic emulsions by .storage at increased temperature or humidity, or both. It is, of course, desirable to have emulsions as stable as possible under the conditions of high temperature and humidity which may occur in tropical climates, for example. Fog usually appears over the Whole area of the sensitive coating, but when severe, it frequentlyis non-uniform. Fog may also be caused by exposure to chemicals, for example, hydrogen sulfide and other reactive sulfur compounds, hydrogen peroxide vapor, and strongly reducing materials. While ,antifoggants and stabilizers may protect, to some extent, against such eifects, it is normally understood ,tha't an antifoggant protects against spontaneous growth offog during pro:- longed storage or storage at high temperatures and humidities, or during development to maximum contrast and speed, or both.

. It is, therefore, an object of my invention to provide certain new tetrazaindene compounds. A further object is to provide methods for. making these new compounds. Still another object is to provide a means of avoiding the aforesaid plumming eifect in photographic prints. Another object is to provide a method of stabilizing photo,- graphic silver halide emulsions during storage. Other objects will become apparent from a consideration -of .the following description and examples. 5 i

It is known that ethyl acetoacetate willjcondense with 3-amin0-122z4-triazole to give a ,tetrazaindene ,derivatirie ice to which the following two alternative formulas have been assigned:

(I) N N (II) N N" It is believed that the product most probably has the structure represented by Formula I, but it is possible :that

the OH group may be attached in the 6-position and the CH group in the 4-position. I shall, therefore, designate the hydroxy-methyl-tetrazaindene obtainable bythe condensation of ethyl acetoacetate with 3-amino-1:2:4-triazole as 4-hydroxy-6-methyl-l:3z3az7 tetrazaindene (Formula I).

It has been found that, in general, acylacetic esters of the general formula:

(III) R COCHR COOC H (IV) H N wherein R represents ahydrogen atom, an alkyl (.i.e.', methyl, ethyl, n-propyl, nbutyl, etc., e.g., an:alkyl group containing from 1 to 4 carbon atoms), an aralkyl (i.e., .benzyl, B-phenethyl, etc.), or aryl (i,e., phenyl, tolyl; chlorophenyl, etc., e.g., a mononuclear aromatic-group of the benzene series), or an alkylthio (e.g., methylthio, ethylthio, etc.), aralkylthio (e.g., benzylthio, etc.), or arylthio (e.g., phenylthio, tolylthio, etc.) group, to give ring-substituted hydroxy 'tetrazaindenes to which the following two alternative.general formulae can be assigned:

wherein R R and R have the values given above.

It is also believed that the products most probably have the structure represented by Formula'V, but it is possible that the OH group may be atta ched in the 6-position and the group R in the 4-position. I shall, therefore, designate the compounds obtainable by this condensation as ring substituents being R R and R It is known that the hydroxyl group in 4-hydroxy-6- methyl-1:3:3a:7-tetrazaindene can be replaced by a chlorine atom and that this chlorine atom can, in turn, be replaced by an amino group or by a substituted amino group; 'It has now been found that the chlorine atom'm this compound, and in compounds obtained by replacement with chlorine of the hydroxyl group in compounds of general Formula V, can be replaced by a mercapto group. It has also been found that the hydroxyl group can be directly replaced by a mercapto group. To the resulting ring-substituted mercapto-tetrazaindenes the following general formula has, in accordance with the considerations indicated above, been assigned.

(YII) The compounds of general Formula V wherein R; is a lingsubstituted 4-hydroxy-l:3:3a:7-tetrazaindenes (the 7 :hydrogen atom can also be directly halogenated to give compounds of the general formula:

represents a halogen atom (e.g., bromine, chlorine, etc.), especially a bromine atom.

The hydroxyl group in the compounds of general Formula VIII can also be replaced by a mercapto group,

7 herein and R, have the values given above, and Hal either directly or by first replacing it by a chlorine atom wherein R and Rghavethe values given above, and Hal represents a halogen atom (e.g., chlorine, bromine, etc.).

It is also known that ethyl acetoacetate will condense with l-amino-l :3 :4-triazole to give a tetrazaindene derivative of the formula:

. V N o /3 It is likewise known that the hydroxyl group in 5- methyl-l:2:-3a:4-tetrazaindene can be replaced by a chlorine atom which in turn can be replaced by a mercapto group to give S-methyl-l:2:3az4-tetrazaindene-7-thiol of the formula:

(XI) H Biilow and Haas, who described the preparation of the compound as well as of the corresponding phenyl cornpound, in Berichte der deutschen chernischen Gesel-lschaft, 1910, vol. 43, 1975, stated that it is easily oxidized. I have found that it-is quite stable and has a melt ing point of 218 C.

It has now been further found that, in general, acylacetic esters of the general formula:

x11 R1COCHR4COOC2H5 wherein R has the values given above, and R represents a hydrogen atom" or an alkyl (i.e., methyl, ethyl, n-propyl,

n-butyl, etc., e.g., an'alkyl group containing froml to 4 carbon atomsfgroup, will condense'with 1-amino-1:3:4-

wherein R represents a hydrogen atom or an alkyl (i.e., methyl, ethyl, n-propyl, n-butyl, etc., e.g., an alkyl group 25-" containing from 1 to 4 carbon atoms), aralkyl (i.e., benzyl, fl-phenethyl, etc.), or ary-l (i.e., phenyl, tolyl, chlorophenyl, etc., e.g., a mononuclear aromatic group of the benzene series) group or an alkylthio (e.g. methylthio,

ethylthio, etc.), aralkylthio (e.g.,-benzylthio, etc.) or arylthio (e.g., phenylthio, tolylthio, etc.) group, to give ring substituted hydroxy-tetrazaindenes of the general formula: n

( IV) i h compounds of the general Formula XIV can be replaced by a chlorine atom and that this chlorine atom can, in ,turn, be replaced by a mercapto (thiol) group. It has also been found. that the hydroxyl group can be directly replaced: by a mercapto group. The resulting mercapto compound has the general formula:

wherein R R and R have the values given above;

It has further been found that a tetrazaindene compound comprising a diazine ring fused to a triazole ring so that said rings have a single nitrogen atom in common and having a. thiol substituent attached to a carbon atom of, said diazine ring, such as the compounds of the general Formulae VII and IXor of the general FormulaXV or thesalt of such a compound, for example, an alkali metal 'salt, can with advantage be incorporated in a photographic silver halide emulsion, or in a photographic treating bath. "It has nowbeen found that by the incorporation in a photographicsilver halide emulsion, especially a silver chloride or chloro-bromide emulsion of at least one tetrazaindene compound comprising a diazine ring fused to a triazole ring so that said rings have a single nitrogen atom in common and having a thiol substituent attached to a carbon atom of said diazine ring, such as the compounds of the probable general Formulae VII'and IX or of the ,aasasss general Formula XV or of -their salts, such imagedegradation can be minimized or even prevented. The compounds are thus effective anti-plumming" agents. They may be directlyincorporated in an emulsion during its manufacture, or the emulsion may be bathed in their solutions in convenient solvents. The emulsion can be a gelatino-silver halide emulsion, but emulsions in which the carrier is polyvinyl alcohol, hydrolyzed cellulose acetate, or other hydrophilic colloid, can be used. When the compounds are incorporated in theemulsiomsuch as a gelatino-silver chloride emulsion containing small amounts of bromide or iodide, they can be used in amounts from 0.2 to 10 grams per unit of silver halide formed from 1000 grams of silver nitrate. When the emulsion is bathed in a solution of the compound, such as an aqueous alkaline solution, the solution can contain from about 0.01% upto about 1%, preferably about v0.1% by weight of the compound.

It has further been found that by the incorporation, in a photographic treating bath, such as a non-coupling developing bath (e.g., a hydroquinone developer) for photographic prints which are to be glazed, of at least one tetrazaindene compound comprising a diazine ring fused to a triazole ring so that said rings have a single nitrogen atom in common and having a thiol substituent attached to a carbon atom of said diazine ring, such as the compounds of the probable general Formulae VII and IX :or of the general Formula XV or of their salts, the reflection density of the maximum blackobtained in the developed print before glazing can be raised, and/or the contrast can be increased. Moreover, by the incorporation in a photographic non-coupling developing bath for photographic transparencies of at least one tetrazaindene compound comprising a ,diazine ring fused to a triazol'e ring so that said rings have a single nitrogen atom in commen and having a thiol substituentattached to a carbon atom of said diazine ring, such as the compounds of the probable general Formulae VII and IX or of the general Formula XV or of their salts, the transmission density of the maximum black obtained on development can be raised, and/ or the contrast can be increased, especially when the transparency is still wet. This is a very useful effechfor example, in X-ray plates.

According to one feature of the present invention, therefore, there is provided a ring-substituted mercaptotetrazaindene of Formula VII or a water-soluble salt thereof, by replacement with the SH group of the --OH group in the ring-substituted hydroxy-tetrazaindene, obtainable by the condensation of an acylacetic ester of I the general formula R COCHR COOC H wherein R and R have the values given above, with a 3-amino-l 2:4- triazole of Formula IV.

1 It will be noted that, owing to the labile character of wherein R has the values given above, with a 3-amino- 1:2:4-triazole of Formula IV).

The replacement of the OH group in compounds of the general Formula V can be effected by well-known methods which are described in the chemical literature. For example, it can be effected by the reaction of phosphorus pentasulphide on a compound of general Formula V. Alternatively, the hydroxyl group can first be replaced by A a chlorine group, for example by the reaction of phosphorus oxychloride and/ or phosphorus pentachloride on a compound of general Formula V, followed by replacement of the chlorine atom by a mercapto group, for example by the action of an alkali metal sulfide, such as potassium sulfide, orthiourea upon the resulting chloro compound.

According to a further feature of the invention, there is provided a compound of Formula XV or a watersoluble salt thereof.

Such compounds can be obtained by replacement with a mercapto group of the hydroxyl'group in compounds of the general Formula XIV by the methods described above for replacement of the hydroxyl group in compounds of general Formula V.

The invention also includes the method of preparing the ring-substituted mercapto-tetrazaindenes of the prob.- able general Formula VII which comprises heating with thiourea in a solvent the ring-substituted chloro-tetrazaindene obtainable by replacement with a chlorine atom of the OH group in the ring-substituted hydroxy-tetrazaindene obtainable by the condensation of an acylacetic ester of the general formula R COCI-IR COOC H wherein R and R have the values given. above, with] a 3-amino-1z2z4-triazole of Formula IV. The said ringsubstituted hydroxytetrazaindene can be heated with phosphorus oxy-chloride, if desired together with phosphorus pentachloride, preferably in the presence of a tertiary organic base such as dimethylaniline, to replace the hydroxyl group with a chlorine atom, and the resulting ring-substituted chloro-tetrazaindene can be heated to reflux with thiourea and methanol to replace the chlorine atom with a mercapto group, the resulting ringsubstituted mercapto tetrazaindene thereafter being isolated from the reaction mixture. 1

The invention also includes the method of preparing the halogeno-ring-substituted mercapto-tetrazaindenes of the probable general Formula IX which comprises heating 'with thiourea in a solvent, the halogeno-ring-substituted chloro-tetrazaindene obtainable by replacement with a chlorine atom of the OH group in the halogeno-ringsubstituted hydroxy-tetrazaindene obtainable by halogenation of the ring-substituted hydroxy-tetrazaindene obtainable by the condensation of an acylacetic ester of the general formula R COCl-I COOC H wherein Ri has the values given above with a 3-amino-l:2:4-triazole of Formula IV. Thus the ring-substituted hydroxy-tetrazaindene obtained by the condensation of an acylacetic ester of the general formula R COCH COOC H wherein R -ha the values given above, with a 3-amino-1:2:4-triazole of Formula IV can be brought into contact, in the form of a suspension or solution, with a halogen, the resulting halogenated compound being then. heated with phosphorus oxychloride, preferably in presence of a tertiary organic base, whereafter the resulting halogeno-ring-substituted chloro-tetrazaindene is heated to reflux with thiourea and methanol and the resulting halogeno-ring-substituted meroapto-tetrazaindene is isolated from the reaction miX- ture. The said suspension or solution may be mixed with a solution of bromine. The solvent may be, for example, acetic acid.

The invention also includes a photographic silver halide emulsion containing at least one tetrazaindene compound comprising a diazine ring fused to a triazole ring so that said rings have a single nitrogen atom in common and having a thiol substituent attached to a carbon atom of said diazine ring, or a salt of such compound.

It also includes a photographic treating bath, such as a with a developer containing at least one of such compounds or their salts. Such tetrazaindene compound is most suitably one of the probable general'Formulae VII and IX or of the general Formula XV. 7 a

The invention will be illustrated by, but is not limited "to, the following examples:

EXAMPLE 1.'6-METHYL-1: 3:3a:7-TETRAZAIN- slowly; After 1 hour the excess phosphorus oxychloride was removed on a steam bath at reduced pressure and the orange oil was poured into a water (1 liter). The tar .dissolved on stirring to give a clear orange solution. This was extracted with chloroform until a sample on evaporation gave no crystalline residue. The chloroform extractwas dried ,over anhydrous sodium sulfate and .the solvent removed under reduced pressure at 50 C.

The crystalline residue was dissolved in hot benzene (200 cc'.) filtered from the orange residue and chilled. The crystals (24.5 gms.) together with a further 3.4 m .-obtained from the filtrate by adding petroleum ether (73% yield) formed flat yellow needles, M.P. 151 C., from benzene.

3.75 gms of 4-chloro-6-methyl-1z3z3az7-tetrazaindene prepared as described above, 1.7 gmsof thiourea and cc. of methanol were refluxed together on a steam bath for 2-3 mins. The thiol separated rapidly. It (3.2 gms. 86.5%) formed orange yellow needles from water, decomposing at 278-279 C; with previous sublimation. Ondissolving it in hot 2 N-sodium carbonate solution and chilling the solution the sodium salt dihydrate crystallized as, paleyellow needles. They are readily recrystallized from hot water and are suitable for use as an'emulsion addendum. They soften at ISO-190 C., tresolidify'and do not melt below 300 C.

I EXAMPLE 6-PHENYL-l:3:3at7-TETRAZAIN- DENE-4-THIOL V /N\ /N mor o o HO s: CH

F SH 4-hydroxy-6-phenyl-lz3:3az7-tetrazaindene (see British specification No. 619,557, Compound No. 5) gms.), dimethylaniline(l8.2 cc.) and phosphorus oxychloride (52 cc.) were heated together at 125 for 1 hour in an oil bath. The solvent was removed under reduced pressure and the residue treated with ice water. The brick-red solid was collected, dried and extracted with benzene. The benzeneextract was concentrated to cc., chilled and the solid, 6.7 gms., M.P. 158, collected.

.This chloro-compound (8 gms.), thiourea (2.8 gms.)

and methanol (30 cc.) were refluxed together for 3 mins. The required thiol separated rapidly. It was collected hot to give 7.9 gms., M.P. 282 C. It was dissolved in hot 2 N-aqueous sodium hydroxide" (20 cc.), filtered and chilled to give a mass of yellow needles of the sodium salt hydrate. It was dissolved in ethanol 10%; Almost immediately it crystallized in the anhydrous form as pale -yellow'needles,-M.P. over 300 C.

EXAMPLE 3.-'-5 -BROMO-6-M ETHYL-1 :3 3a: 7-'IET- RAZAINDENE-4-THIOL N H30 2; (i1 \CE I Br- N N/ 0 SH 4-hydroxy-6-methyl-1 :3 :3az7-tetrazaindene (15 gms.) was. suspended in acetic acid (100 cc.) and treated at 20 C. with a solution of bromine (5.2 cc.) in acetic acid (20 cc'.). The suspended crystals dissolved "and the S-bromo derivative crystallized. Water (250 cc.) was added and the crystals were collected. It (18 gms.) was dissolved in hot aqueous 0.2 N-sodium carbonate '(1 liter) and acidified slowly with dilute hydrochloric acid. An excess of triethylamine was added to dissolve any unchanged starting material and the crystals were collected. From water it formed whitefneedles, M.P. 269 C.

The bromo-derivative (22.9 gms.) was treated with dimethylaniline (15 cc.) and phosphorus oxychloride cc.) at 125 C. for 1 hour. dissolved so phosphorus pentachloride' (20.8 gms.) was then added and the heating continued for 2 hours. The solvents were removed by distillation and the residue treated with ice-water and extracted with chloroform. Removal of the dried chloroform left a black solid. Thiourea (8.0 gms.) and methanol (50 cc.) were added and the whole was refluxed for 5 minutes. A dark.

correctly for the required thiol.

EXAMPLE 4. 2:6-DIMETHYL-1z3z3az7-TETRAZA- INDENE-4-THIOL 3- amino-5-methyl-1:2:4-triazole (47 gms.), 'ethyl acetoac'etate (65-7 gms.) and acetic acid (200 cc.) were refluxed together for 3 hours. The 4-hydroxy-2z6-dimethyl 1:3:3a:7 tetrazaindene separated on chilling.

. From water (charcoal) it (33 gms.) formed white needles',,M.P. 307 C.

'It (33 gms.) was treated at 125 C. for 1 hour with phosphorus oxychloride cc.) and dimethylaniline (31.5 cc.) and the solvents were removed. The residue was treated with ice-water, filtered and the filtrate was extracted with chloroform. The dried chloroform was distilled off and the residual solid (20.4 gms., M.P. 148 C.) refluxed with thiourea (8.7 gms.) in methanol cc.) for 3 minutes. The required thiol separated rapidly. It (17 gms.) was recrystallized from water to form yellow needles, M.P. 286 C. (decomp'.).

EXAMPLE 5.-6 METHYL 2 METHYLTHIO- l :3 3 a 7-TETRAZAINDENE-4-THIOL The solid only partly 9 4 hydroxy 6 methyl 2 methylthi o 1:3:3az7- tetrazaindene (22 gms.), dimethylaniline (17.4 cc.) and phosphorus oxychloride (50 cc.) were heated together in an oil bath at 125 C. for 1 hour. The solvents were removed and the residue treated with ice-water and extracted with chloroform. The dried chloroform extract was distilled to remove solvent and the residue recrystallized from ethanol. It (11:5 gms.) (M.P. 113-116 C.), thiourea (4.1 gms.) and methanol (50 cc.) were heated together for 3 minutes on a steam bath. The thiol crystallized during this time. From ethanol it (5.3 gms.) formed light yellow crystals, M.P. 265 C.

.EXAMPLE 6. -ETHYL-6-METHYL-lz3:3a:7-TET- RAZAINDENE-4-THIQL Ethyl ethylacetoacetate (100 gms.), 3-arninol:2:4- ,triazole (50 gms.) and acetic acid' (250 cc.) were refiuxed for 3 hours, the solution was chilled and the crystals collected. The crystals had MLP. 275 C. and weight 49 gms. It is 5 ethyl 4 hydroxy 6 methyl- 1:3;3a27-tetraxaindene. It (48 gms.), dimethylaniline (41.5 cc.) and phosphorus oxychloride (120 cc.) were heated in an oil bath at 125 C. for 1 hour. The solyenft was distilled off and the residue after treatment with ice-water was taken up in chloroform, the solution was drie d andthe solvent distilled off. The residue (40.9 gms.) of chloro-compound formed yellow-needles, M.P. 132 C., from ethanol.

It (40.9 gms.), thiourea (15.9 gms.) and methanol (150 cc.) were refluxed together for 3 minutes. The solid which separated (43 gms.) formed yellow needles, M.P. 270-273 C., from ethanol.

EXAMPLE 7. 5-ISO-BUTYL-6-METHYL-l:3:3a:7-

TETRAZAINDENEA-THIOL .a -lsq-hutylacetoacetie ester (0.1 mol.) and 5-aminolz 2z4-triazole (0.1 mol.) were refluxed together in glaacetic acid (40 cc.) for 7 hours. On cooling the product was precipitated by the addition of water. It (5 ispbutyl 4 hydroxy 6 methyl 1:3:3az7 tetraaindene) was recrystallized from water as colorless needl'es, M.P. 258 C. (yield 60%).

The above'(6gms;), dimethyl aniline (6 gms.). and

phosphorus oxychloride (18 gms.) were refluxed together at 125 C. for 4 hours, after which the excess oxychlor ride was removed under vacuum, and the residue poured onto crushed ice and extracted with chloroform. After drying, the solvent was removed and the resulting dark oil (5 gms.) (4-chloro-5risobutyl-6rmethylelz3z3az7-tete ragaindene) used without further purification.

It (4 gms.) and ,thiourea (1.4 gms.) were refluxed together in ethanol for 2 hours during which time a; yellow crystalline solid separated. After cooling the product was collected and washed while still on the filter with a i 10 .EXAMRLB 5PPHENYLJ=ZI3Q14JETRAZAIN DENE-7-THIOL Ethyl benzoylacetate (96 gms.) and 1-amino-1z3z4- triazole (42 gms.) were fused at l-l80 C. forl hour. Ethanol (25 cc.) was added to the orange melt to give a crystalline cake. It (21 gms.) formed cream needles, M.P. 284 285 C., from aqueous ethanol. It (20.8 gms.), dimethylaniline (15 cc.) and phosphorus oxychloride (55 cc.) were heated togetherinan oil bath at C. for 1 hour. On removing'the solvent the whole solidified. It was shaken with ice-water and chloroform and the dried chloroform layer evaporated to dryness. The solid was dissolved in benzene, filtered and the solution was chilled to give 12.8 grns. (56.5%) yield of chloro-compound. It formed straw-colored needles, M.P. 214 C.

The chloro-compound (10.9 gms.) was covered with a solution of potassiumhydroxide (20 gms.) in water (200 cc.) which had been saturated with hydrogen sulfide. Ethanol (200 cc.) was then added and the whole brought to the' boil. The sqlid dissolved and the filtered solution was then acidified with dilute hydrochloric acid. Ih na e yello fle ke wh h pre i a were e ystallized from ethanol. The required thiol (9.3 gms.) formed soft yellowneedles, M.P. 173 C. (resolidilied and then M.P., 250

EXAMPLE. 9.6 ETHYL s METHYL 1:21am TEThAZAINDEN-E'J THIOL chloride, (1 12 cc.) were heated for 1 hour at 125 C.

The solvent was distilled off at reduced pressure. The residue wasdecomposed with ice-water and chloroform. The aqueous phase was extracted with chloroform and the combined extracts dried and the solvent removed. The residual chloro-compound (colorless needles, M.P. 112 C., from ethanol) was then treated with potassium hydro-- gen sulfide as in Example 8. The required thiol formed. glistening yello'w'plates', M.P. 23.8. 'C., from ethanol.

EXAMPLE 10.5 METHYL 1:2:3a:4 TETRA- ZAINDENE-7-THIOL This was made as described by Biilow and Haas (10c. cit.), M.P.218 C.

The following data will serve to illustrate the uniqueefie Obtained wh n o he memento comp nds of my invention is incorporated in a photographic silver halide emulsion prior to coating on a conventional sup- EQU: The a e Mh o lo ing abl e ebt y eaee u e emule eas he ueual. man e f lo ed by develeeies. a ts washin -j The tesulting printsunseen were then hot-glazed in the usual The following data were obtained:

Table A.-Silver chloride emulsion Table B.Silver bromide emulsion [Compound incorporated at rate or 0.1 gm. per mol AgBn] Maximum Density Compound Contrast Original Hot 7 p glazed None 2.8 1.81 1.56 1 g 1.81 1.70 I 3.1 1.81 1.69 ,Ex. 6 3.5 1.84 1.76

' Table jC.Silver chloride emulsion [Compound incorporated atrate 010.5 gm. per mol kigCL] I t Q Maximum Dam.

Compound Contrast f Original H glazed 'i-&n.-;-.'.--;' 5.7 1. as 1.35 7.6 1.63 1.62

Maximum Denslty Compound Contrast Original 7 Hot 4 l I "glazed Ntt. 1.7a 1.07 1.56 Ex. 10 1.80 1.68 1.64

- Table E.Silver chloride emulsion [Compound incorporated at rate of 1.0 gm. per mol AgCL] H 'ltdaximumDensity Compound Contrast i Original Hot glazed NCIIB......-;'. 8.8 1.75 1.59 EX.8..--.,.. 8.8 1.75 1.10

Table F.Silver. bromide emulsionj [Compound incorporated at rate oi 0.1 gm. per mol AgBr.)

Maximum Density Compound .Contrast Original Hot glazed None; 1? as m 1.56 Ex.9 3.6 1.84 1.76

The data in the following tablewereobtained by treating an exposed ordinary X-iay emulsion (such as. a silver bromiodideeriiulsion) with an aqueous sodium'carbonate 12 solution containing one of the compounds prepared in the examples, the concentration of the tetrazaindene compound being given in the table. After treatment of the eripos ed emulsion with the aqueous alkaline solution it I was developed in the usual manner.

. Tab le G.'Pretreatment of X-ray emulsion As indicated above, many of the tetrazaindene compounds of my invention are useful in stabilizing photographic silver halide emulsions, and in particular, highspeed negative emulsions. The amount of tetrazaindene compound required to stabilize the emulsion can be determined in the usual manner by incorporating varying amounts of stabilizer in a series of emulsions. The test strips can then be stored under conditions of constant temperature and humidity, before the test strips are exposed and developed. In general, storage for a period of about two weeks at 120 F. is sufiicient to accelerate the formation of fog.

In the following table, the'antifoggant and stabilizing action were determined by incubation of the emulsion for two weeks at a temperature of 120 F. and constant relative humidity (obtained by placing the emulsions in closed containers, the room temperature being about 70 F. and relative humidity about 55% prior to scaling the containers).

The efiiciency of the various antifoggants was determined by measuring the speed, gamma and fog of "the incubated emulsions containing an antifoggant and comparing these measurements with those of the same batch of emulsion before incubation. Also, similar measurements were made with a photographic emulsion containing no antiioggant, both before and after incubation.

The tests were made using high speed, negative-type silver bromiodide emulsions (coated on cellulose acctate supports), which had been panchromatically sensitized with a cyanine dye and chemically sensitized with silver and gold compounds. 7 r 7 The test films were exposed for 1& second on an intensity scale sensitometer (Eastman Ib type) and developed for five minutes in a developer having the following composition: I

Water to make 1 liter.

The speed, gamma and fog for each of the emulsion coatings were then measured as indicated above. 'I'hespeed figure (CR) shown in the following table is on a loga rithmic scale, obtained by the formula:

(1 minus log E) where E is the exposure in meter-candle-seconds of sunlight quantity required to produce a density of 0.30 above fogl. The results obtained are given 7 in the .gfollowing ta e. t

creases Table Fre'sh Coatings Incubated'Z Weeks, 120 F. Addenda Oomg./mo1.

und A 1 CR 1 Fog Speed 7 Fog Speed When using the compounds ofqmy invention for the purpose of stabilizing photographic silver halide emulsions in accordancewith the above directions, it is convenient to employ from about 5 to 100mg per mol. of silver halide in the emulsion.

The term; thiol or mercapto as us din the foregoing specification and the following claimsis intended to mean; not only --SH, but also water-soluble salts thereof, such as sodium,,potassium, ammonium,- organic ammonium, etc. salts. t

What I claim asmy' invention anddesire secured by Letters Patent of the United States is: r r

1. The method of preventing image degradation of an exposed silver halide emulsion during processing which comprises performing at least one of the steps of developing, fixing, washing and drying said emulsion in the presence of a compound selected from those represented by the following general formula:

wherein R represents a member selected from the group consisting of an alkyl group containing from 1 to 4 carbon atoms, an aralkyl group containing from 7 to 8 carbon atoms, and a mononuclear aromatic group of the benzene series, R represents a member selected from the group consisting of a hydrogen atom, an alkyl group containing from 1 to 4 carbon atoms, an aralkyl group containing from 7 to 8 carbon atoms, a mononuclear aromatic group of the benzene series, an alkylthio group containing from 1 to 2 carbon atoms, an aralkylthio group, and an arylthio group containing from *6 to 7 carbon atoms, and R represents a member selected from the group consisting of a hydrogen atom, a halogen atom and an alkyl group.

2. The method of preventing image degradation of an exposed silver halide emulsion during processing which comprises performing at least one of the steps of developing, fixing, washing and drying said emulsion in the presence of avcompound selected from those represented by the following general formula:

wherein R represents a member selected from the group consisting of an alkyl group containing from 1 to 4 carbon atoms, an aralkyl group containing from 7 to 8 carbon atoms, and a mononuclear aromatic group of the benzene series, R represents a member selected from the group consisting of a hydrogen atom and an alkyl group co'ntainingfrom 1 to 4 carbon atoms, andRg'rep resents amember selected from the group consisting of a hydrogenatom, an alkyl group containing from 1 to 4* carbon atoms, an aralkyl group containing from 7 to 8 carbon atoms, a' mononuclear aromatic group of the benzene series, an alkylthio group containing from 1 to 2 carbonatomaan aralkylthio group, and an arylthio group containing from 6 to 7 carbon atoms.

3'; The method of preventing image degradation ofan exposed silver halide emulsion during processing which comprises incorporating in at leastone of the developing, fixing and washing baths used to process said emulsioma compound selected from those-represented by the following general formula:

containing from 1 to 4' carbon atoins, an aralkyl group containing from 7 to 8 carbon atoms, a mononuclear aromatic group of the benzene series, an alkylthio group containing from 1 to 2 carbon atoms, an aralkylthio group, and an arylthio group containing from 6 to 7 carbon atoms, and R represents a member selected from the group consisting of a hydrogen atom, a halogen atom and an alkyl group.

4. The method of preventing image degradation of an exposed silver halide emulsion during processing which comprises incorporating in at least one of the developing, fixing and washing baths used to process said emulsion, a compound selected from those represented by the following general formula:

wherein R represents a member selected from the group consisting of an alkyl group containing from 1 to 4 carbon atoms, an aralkyl group containing from 7 to 8 carbon atoms, and a mononuclear aromatic group of the benzene series, R represents a member selected from the group consisting of a hydrogen atom and an alkyl group containing from 1 to 4 carbon atoms, and R represents a member selected from the group consisting of a hydrogen atom, an alkyl group containing from 1 to 4 carbon atoms, an aralkyl group containing from 7 to 8 carbon atoms, a mononuclear aromatic group of the benzene series, an alkylthio group containing from 1 to 2 carbon atoms, an aralkylthio group, and an arylthio group containing from 6 to 7 carbon atoms.

5. A photographic silver halide emulsion containing a compound selected from those represented by the following general formula:

wherein R represents a member selected from the group consisting of an alkyl group containing from 1 to 4 carbon aeasgsss atoms, an aralkyl group containing from 7: to 8 carbonatoms, and a mononuclear aromatic group 'of .thebenzene series, R represents a member selected from the group consisting of a hydrogen-atom, an alkyl' group contain-: ing from 1 to 4 carbon atoms, an aralkyl group contain. ing from 7 to 8 carbon atoms, a mononuclear aromatic group of the benzeneseries, an alkylthio group containing:

wherein R represents a member selected from group consisting of an alkyl group containingfrom 1 to 4 carbon atoms, an aralkyl group containing from 7to 8 carbon atoms, anda mononuclear aromatic group of the 51B benzene series, R; representsfa'i'member selected from the group consisting ofa hydrogen atom and an alkyl. group containing from 1 to 4 carbon atoms, and R represents a member selected from the group consisting of a hydrogen atom, an alkyl group containing from 1 to 4' carbon atoms, an aralkyl group containing from 7 to 8 r n t ms a mononuclear r ma??? roup. o benzene series, an alkylthio group containing from 1 to 2 carbon atoms, an aralkylthio group,'jand"an'arylthio group containing from 6 to -7 carbon atoms p -7. A photographic silver halide deyeloping' gntemul sion containing 6 -rnethyl-lz3:3az74etrazaindene-4-thiol.I 8. A photographic silver-halide developing-put 'emul-' sion containing 5: 4 bromo 6 methyl-1 :3 3az7-tetrazain dene 4 thiol. Y 4.. t. 9. A photographic silver halide developing out eniul-" sion containing 2: 6-dimethyl-l :3 3az7gtetrazaindene 4- tbjoL. U "i i I; I

' 10. 'A photographic silver halide developing-out en'rul sic-1 containing 5-ethyl-6-me'thyl-1:3-3a:7-tetrazaindene 4. 0L 1" ll.,; '11. A photographic silver halide developing-out sion containing 2-phenyl-1:2z3az4-tetrazaindene-7-thioh' References Cited inthe'file of this patent I FOREIGN PATENTS a,

Canada' Mai; '29, 19 191 I? 

1. THE METHOD OF PREVENTING IMAGE DEGRADATION OF AN EXPOSED SILVER HALIDE EMULSION DURING PROCESSING WHICH COMPRISES PERFORMING AT LEAST ONE OF THE STEPS OF DEVELOPING, FIXING, WASHING AND DRYING SAID EMULSION IN THE PRESENCE OF A COMPOUND SELECTED FROM THOSE REPRESENTED BY THE FOLLOWING GENERAL FORMULA:
 2. THE METHOD OF PREVENTING IMAGE DEGRADATION OF AN EXPOSED SILVER HALIDE EMULSION DURING PROCESSING WHICH COMPRISES PERFORMING AT LEAST ONE OF THE STEPS OF DEVELOPING, FIXING, WASHING AND DRYING SAID EMULSION IN THE PRESENCE OF A COMPOUND SELECTED FROM THOSE REPRESENTED BY THE FOLLOWING GENERAL FORMULA: 